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701.
Elina Sjman Mika Mnttri Marianne Nystrm Hannu Koivikko Heikki Heikkil 《Journal of membrane science》2008,310(1-2):268-277
Xylose is an intermediate product in xylitol production. Nanofiltration could simplify and enhance this separation step conventionally done by chromatographic methods. Here different hemicellulose hydrolyzate feeds were nanofiltered to recover xylose into the permeate.Two different batches of hemicellulose hydrolyzate were prepared: the hydrolyzate as such and modified with crystalline xylose addition. Both feed solutions were diluted to a total dry solids (TDS) content of approximately 21 wt.% and the xylose contents were 48.7% and 59.1% of the TDSf (total dry solids in feed). The filtration experiments were made at 40, 50 and 60 °C in total reflux mode for approximately 30 min at each pressure of 20, 25, 30, 35 and 40 bar. In addition, a 20-h filtration was made at 50 °C and 30 bar. A DDS LabStak M20-filter was used and it was equipped with Desal-5 DK, Desal-5 DL and NF270 membranes.In short-term filtrations, the nanofiltered permeate of the original hydrolyzate had 78–82% xylose of the TDSp (total dry solids in permeate) and the modified hydrolyzate 86–88% xylose of the TDSp. Thus, considerable xylose purification was obtained. The addition of crystalline xylose into the hemicellulose hydrolyzate gave a notable increase in permeate fluxes. The 20-h filtration showed fouling and compaction effects as a flux decrease of approximately 10–25% was detected in the retention integrity test. According to the results, xylose purification from hemicellulose hydrolyzate could be enhanced by nanofiltration. 相似文献
702.
Silicon dioxide (SiO2) nanoparticles were incorporated into Nafion 115 membranes using the sol–gel method in order to investigate their effect on water retention/transport, proton concentration, effective proton mobility, and proton conductivity. By adjusting the sol–gel reaction time, Nafion/SiO2 membranes were fabricated with SiO2 content ranging from 5.9 to 33.3 wt%. Because the density of the membranes decreased with increasing SiO2 content and because dimensional changes with swelling in water of the composite membranes were less than that of unmodified Nafion 115 despite having increased water content, the theory that rigid scaffolding is formed inside the membrane is supported. Water content increases with increasing SiO2 content due to void space formed inside the membrane. This increase in water content dilutes the protons in the membrane leading to lower proton concentration and therefore lower proton conductivity. A decreasing effective proton mobility with increasing SiO2 content, likely due to an increase in the tortuosity of the proton-conducting pathway, also contributes to the decreasing conductivity. However, as evidenced by the similar water vapour permeance values, the SiO2 nanoparticles do not increase the effective tortuosity of the water vapour transmission pathways. 相似文献
703.
Rousseau A Pedrini M Chiap P Ivanyi R Crommen J Fillet M Servais AC 《Electrophoresis》2008,29(17):3641-3648
A nonaqueous capillary electrophoresis (NACE) assay was developed for the separation and determination of flurbiprofen enantiomers in plasma samples using 6-monodeoxy-6-mono(3-hydroxy)propylamino-beta-cyclodextrin as chiral selector. The nonaqueous background electrolyte was made up of 40 mM ammonium acetate in methanol (MeOH), and flufenamic acid was employed as internal standard. Solid-phase extraction was used for sample cleanup prior to the NACE separation. The NACE method reproducibility was optimized by evaluating different capillary washing sequences between runs. After having tested various conditions, trifluoroacetic acid (1 M) in MeOH was finally selected. Concerning the solid-phase extraction procedure, good and reproducible analyte recoveries were obtained using MeOH for protein denaturation and a polymeric phase combining hydrophobic interactions with anion exchange properties (Oasis) MAX) was selected as extraction sorbent. The method selectivity was not only demonstrated toward a blank plasma sample but also toward other non-steroidal anti-inflammatory drugs. The method was then successfully validated with respect to response function, trueness, precision, accuracy, linearity and limit of quantification. 相似文献
704.
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706.
Emanuela S. Fioretta Joost O. Fledderus Ewelina A. Burakowska‐Meise Frank P. T. Baaijens Marianne C. Verhaar Carlijn V. C. Bouten 《Macromolecular bioscience》2012,12(5):577-590
In situ vascular tissue engineering has been proposed as a promising approach to fulfill the need for small‐diameter blood vessel substitutes. The approach comprises the use of a cell‐free instructive scaffold to guide and control cell recruitment, differentiation, and tissue formation at the locus of implantation. Here we review the design parameters for such scaffolds, with special emphasis on differentiation of recruited ECFCs into the different lineages that constitute the vessel wall. Next to defining the target properties of the vessel, we concentrate on the target cell source, the ECFCs, and on the environmental control of the fate of these cells within the scaffold. The prospects of the approach are discussed in the light of current technical and biological hurdles.
707.
Daziano JP Günther WH Krieg M Tsujino I Miyagi K Anderson GS Sampson RW Ostrowski MD Muir SA Bula RJ Sieber F 《Photochemistry and photobiology》2012,88(2):448-460
The objective of this study was to determine if and how photoproducts contribute to the antitumor effect of merocyanine-mediated PDT. A panel of barbituric, thiobarbituric and selenobarbituric acid analogues of Merocyanine 540 was photobleached, and the resulting photoproducts were characterized by absorption, fluorescence emission, mass, energy dispersive X-ray, and X-ray photoelectron spectroscopy and tested for cytotoxic activity against tumor cell lines and freshly explanted bone marrow cells. While all dyes were readily photobleached, only photoproducts of selone dyes showed cytotoxic activity. One-hour incubations with micromolar concentrations of selone-derived photoproducts were sufficient to reduce leukemia/lymphoma cells ≥10 000 fold, whereas preserving virtually all normal CD34-positive bone marrow cells. Of six multidrug-resistant tumor cell lines tested, five were as sensitive or more sensitive to photoproducts than the corresponding wild-type lines. Physicochemical characterizations of the cytotoxic activity indicated that it consisted of conjugates of subnano particles of elemental selenium and (lipo)proteins. The discovery of cytotoxic Se-protein conjugates provides a rare example of photoproducts contributing substantially to the antitumor effect of PDT and challenges the long-held view that Se in oxidation state zero is biologically inert. Agents modeled after our Se-protein conjugates may prove useful for the treatment of leukemia. 相似文献
708.
Marini RD Groom C Doucet FR Hawari J Bitar Y Holzgrabe U Gotti R Schappler J Rudaz S Veuthey JL Mol R Somsen GW de Jong GJ Ha PT Zhang J Van Schepdael A Hoogmartens J Briône W Ceccato A Boulanger B Mangelings D Vander Heyden Y Van Ael W Jimidar I Pedrini M Servais AC Fillet M Crommen J Rozet E Hubert P 《Electrophoresis》2006,27(12):2386-2399
709.
The coupling of CE with MS detection, a relatively recent hyphenated technique, has gained increasing respect in the field of bioanalytical applications over the past few years. The first part of this review presents CE-MS applications dealing with drug bioanalysis, including forensic analysis and metabolism studies. Practical considerations to achieve a robust and sensitive CE-MS coupling are also presented. It is indeed essential to strictly control some critical electrospray parameters, such as the sheath liquid composition and flow rate, the nebulizing gas pressure as well as the capillary outlet position. The second part of the review critically describes the applications of CE coupled on-line to MS for the identification of biomarkers in body fluids for diagnostic purposes. Since the sample preparation procedures strongly differ according to the intended use (drug bioanalysis or biomarker discovery), they are discussed separately, taking into account the particular properties of plasma and urine matrices. 相似文献
710.
Falsig H Gross A Kongsted J Osted A Sloth M Mikkelsen KV Christiansen O 《The journal of physical chemistry. A》2006,110(2):660-670
We present a study of the interaction between a phenol molecule and an aerosol particle. The aerosol particle is represented by a cluster of 128 water molecules. Using a classical approach, we present interaction energy surfaces for different relative distances and for three orientations of phenol relative to the particle. From the energy surfaces we find the reaction pathways with the largest interaction between the molecule and the particle. We use a quantum mechanics/molecular mechanics (QM/MM) method to calculate a potential energy curve for each reaction path. Coupled cluster methods are used for the part of the system described by quantum mechanics, while the part described by molecular mechanics is represented by a polarizable force field. We compare results obtained from the classical approach with the QM/MM results. Furthermore, we use the QM/MM results to calculate mass accommodation coefficients using a quantum-statistical (QM-ST) model and show how the mass accommodation coefficient depends on the relative orientation of phenol with respect to the aerosol particle. 相似文献